How is Extraction meant to work?

[Matchstickman]

Or when do you get your free "withdraw" attacks?

A	B	C
	1	2	3	4
	5

A, B and C are enemies and you are engaged in melee with them, in spot 1.
It is your turn and you want to move away. If you move to spot 5 you will suffer 3 "withdrawal" attacks, what happens if you move to spot 4? Do you suffer 3 attacks when you arrive at spot 4 or one at each spot along the path (A's attack at 2, B's attack at 3 and C's attack at 4)?
How does that change if you have Extraction? Is Extraction meant to reward tactical movement or is it meant to "prevent" only a single attack per turn?

More generally, if you withdraw from different engagements/multiple times during a single turn, does Extraction "prevent" one attack from each engagement or only one attack per turn (or is it per round)?

[PEGClint]

Or when do you get your free "withdraw" attacks?

A	B	C
	1	2	3	4
	5

A, B and C are enemies and you are engaged in melee with them, in spot 1.
It is your turn and you want to move away. If you move to spot 5 you will suffer 3 "withdrawal" attacks, what happens if you move to spot 4? Do you suffer 3 attacks when you arrive at spot 4 or one at each spot along the path (A's attack at 2, B's attack at 3 and C's attack at 4)?

Neither. It's not about the character's endpoint, it's the fact they are retreating from melee. Per Withdrawing From Melee (italics added), "Whenever a character retreats from melee...opponents get an immediate Free Attack."

So once the character's intent is to move to point 5 or point 4, A, B, and C get their attacks as soon as the character begins their movement in space #1.

How does that change if you have Extraction? Is Extraction meant to reward tactical movement or is it meant to "prevent" only a single attack per turn?

Extraction would prevent one of the three attacks.

More generally, if you withdraw from different engagements/multiple times during a single turn, does Extraction "prevent" one attack from each engagement or only one attack per turn (or is it per round)?

If on their turn, the character with Extraction moves "away from adjacent foes, one of them (player’s choice), doesn’t get his free Fighting attack." So it's one attack per turn for the character.

Hope that helps.